The present disclosure relates to the electrical, electronic, and computer arts, and, more particularly, to methods for providing high gallium doping in high-Ge percentage silicon germanium substrates without carbon incorporation, and structures obtained by such methods.
High doping levels are desirable in various elements of electronic semiconductor devices such as FinFET devices. Silicon germanium is often preferred to silicon within such devices to facilitate the performance thereof. Silicon germanium having germanium content of at least eighty-five percent (85%) has a band structure close to pure germanium. Channel materials including high germanium content offer potential for developing 7 nm and later nodes.
Source/drain regions, contact regions and some other elements found in semiconductor devices used to form integrated circuits are doped with n-type and/or p-type dopants. Boron-doped silicon germanium source/drain regions can, for example, be employed within pFETs. The solid solubility of boron in high percentage silicon germanium alloys (Si1-xGex where x is 0.85 or greater) is, however, low. Gallium is a p-type dopant with higher solubility in high percentage silicon germanium than boron. Due to the tight architecture of some device structures, gallium implantation is not always a viable option. In situ doped epitaxial processes using metal-organic gallium precursors lead to carbon incorporation, which is undesirable as it increases resistance.